Conventionally, in an appearance inspection, an appearance of a manufacture is imaged by using an imaging device such as a camera, and presence or absence of a defect is determined. Specially, in a Factory Automation (FA) field, noise, a shadow, a luminance change, and the like occur in an image depending on an imaging environment. Hence, a robust process is desired with respect to an environmental change for an image processing algorithm which finds a defective part. While operating the appearance inspection apparatus, the environmental change may be caused when a target to inspect is changed or the appearance inspection apparatus is improved. In this case, the image processing algorithm is re-developed. In order to reduce its workload, it is desired to easily re-develop the image processing method.
As one of methods for automatically generating an image processing algorithm, Automatic Construction of Tree-structural Image Transformation (ACTIT) has been proposed in which genetic programming is adapted to an image processing. In this method, it is considered that an image processing scheme forms a tree structure. An input image and an image of a process result to be a target (target image) are prepared. By using the genetic programming, the tree structure is optimized for an image processing filter group which has higher fitness to a target process.
[Non-Patent Document 1]    ACTIT: Automatic Construction of Tree-structural Image Transformation, the Journal of the Institute of Image Information and Television Engineers 53, 6, pp 888-894, 1999
In the ACTIT as related art, in order to represent a complicated process by the tree structure, types of image filters which correspond to base of a filter structure become wider, and a depth of the tree structure become greater. Due to a wider range of types of the image filters and a greater depth of the tree structure, combinations of the filter structures exponentially become greater. That is, a search range becomes wider, and a performance of searching for a target image processing is degraded.